1. Field
The present disclosure relates generally to processing radar images and, in particular, to detecting targets within radar images. Still more particularly, the present disclosure relates to a method for distinguishing between maritime targets and clutter within radar images.
2. Background
Radar systems are widely used in performing operations such as, for example, without limitation, target detection, target tracking, traffic monitoring, weapon targeting, and other types of operations. In particular, radar systems are oftentimes used in performing maritime operations such as, for example, without limitation, ship detection, ship tracking, ship traffic monitoring, and other types of maritime operations.
For example, a radar system may be used to generate one or more radar images that may, in turn, be used to detect the presence of one or more objects of interest. The radar images generated may be, for example, range-Doppler maps. As one illustrative example, a radar system, such as a synthetic aperture radar (SAR) system, may be mounted to an unmanned aerial vehicle (UAV) or some other type of aircraft. The synthetic aperture radar system may be used to generate range-Doppler maps of the sea as the unmanned aerial vehicle flies over the sea. These range-Doppler maps may then be used to detect the presence of objects of interest at sea such as, for example, ships. In some cases, these range-Doppler maps may be used to track the movement of objects of interest over time.
As used herein, a “target” in a range-Doppler map represents an object of interest that the radar system is intended to detect. Oftentimes, a target, such as a ship, appears as a bright vertical line in a range-Doppler map. However, clutter may also appear as one or more bright vertical lines in a range-Doppler map. Consequently, distinguishing between targets and clutter may be more difficult than desired.
As used herein, “clutter” in a range-Doppler map includes any indications within the range-Doppler map that do not represent the object of interest. Clutter may be caused by any number of factors. For example, clutter may be generated in response to undesired contributions to the return signal received by the radar system. Further, clutter may be generated in response to, for example, without limitation, object echoes, jamming signals, noise, unintentional interference, atmospheric interface, sea clutter such as moving sea wave crests, and/or other types of contributions.
Some currently available image processing techniques may be unable to distinguish between targets and clutter with a desired level of accuracy. For example, some currently available image processing techniques use line detection and adaptive thresholding to detect targets. However, these techniques may produce a higher rate of false detections, or false alarms, than desired. Consequently, the detections made by these types of image processing techniques may be less useful than desired for ship detection, ship tracking, and/or other types of applications. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.